It is well known to defat soybeans by extraction with solvents such as hexane and to use the defatted protein containing residue in the preparation of various food products. Soybeans defatted commercially by the presently accepted art generally contain 1 to 5 percent total lipid and a residue of bound fat, principally phospholipid, amounting to about 1 percent or more. However, it is this residual bound fat that is responsible for much of the residual off-flavor or beaniness and instability in the product. While certain of the prior art extraction procedures have been partially successful in eliminating the characteristic bitter soybean taste, the defatted residue still contains an undesirable mouth-coating factor (or substance), also described as a lard-like taste which sticks in the throat.
It additionally was discovered and disclosed in U.S. Pat. No. 3,721,569, to Steinkraus, which is hereby incorporated by reference, that the residual bound fat including the mouth-coating factor along with remaining bitterness could be removed by extraction with ethyl alcohol together with or followed by extraction with chloroform.
It is the object of the present invention to provide an improved process for producing soybean flakes which are defatted and debittered, which also removes the undesirable mouth-coating factor and produces a product with improved aqueous solubility substantially free of phospholipid.
These and other objects and advantages of the present invention will become apparent on consideration of the extractive methods more fully described in the discussion and examples which follow.